That silence you hear? 
That's the blissful silence of a room not full of 11 to 16 year old children. 
Because they just ran through half of the museum like a swarm of whooping vermin and are now two rooms away.

Dear teacher, if you have just entered the room and are greeted by blissful silence, that's probably an indicator that your students are in another room.

If your students are in another room, you are no longer accompanying them on their visit.
Now is not the time for you to take a slow and gentle stroll, engrossed in each cabinet's contents.

Please don't look at me like that when I ask you to be in the same room as them.
It's not my fault that you bought a group of howler monkeys into a public space, who glared at me with barely veiled disdain and amusement when I asked them to stop running and shouting, and pointed out all of the glass hazards and other visitors.

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Asking your oldest student to make sure the others don't go into the third room is a sort of solution.
Half your students are now accompanied, the other half are now only one room away. Which is an improvement.

Eight students are leaning on a set of doors, obeying "Don't go in that room yet" while also forming an attractive barricade.

There are another couple chasing each other in circles around a glass cabinet.

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There's no education session or tour arranged, but trying to get them on board with not just running and yelling is worth a try.

Attempts to engage them in looking at things and taking an interest in anything for more than ten seconds is greeted by sullen silence, or flickering mayfly attention spans accompanied by yelled exclamations, or flat out walking away to annoy each other.

The teacher, now in the room, is vaguely apologetic, and haphazard in any attempt to regain control.
Yes, they are obviously enjoying themselves. But not really in any way I'd describe as positive.
Shouting "That looks like your minger sister! Minger! Minger! Minger!" is, in a way, engaging with the exhibits.

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Hang on, those six kids in the cafe... Oh, so they are part of the school group, but were slow eating lunch and the teacher decided they could catch up once finished.
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Shall we revisit - If your students are in another room, you are no longer accompanying them on their visit?

This teacher was amazing.
He had read the educational visits advice. 
He had already set the kids up to follow it.
He had equipped all of the kids with a clipboard, pencil and paper, so he could set them quick little tasks to keep them occupied if they started to get bored in the museum. 
"I think I love you" was actually said to him, with ensuing explanation about how he'd exceeded usual expectations. 

One child has visited before and knows where a real dead skeleton is.
All other exhibits in the museum can wait.
As can the teacher.

I doubt that when using her own clothing to illustrate a part of the session, the education lady expected to get 'zinged' by a child of about 6.

When working with children, always think for a second "How could they respond to this in a way which is rude, silly, bewildering or insulting?" Then accept that there are many things they will say which you will never be able to mentally prepare for, and learn how to maintain a pleasant but firm demeanor no matter what happens.

Few things can shake your soul like a child of six staring you straight in the face, with the clear conviction that they purposefully and maliciously intend to derail your entire education or creative session. And the whimpering knowledge that one way or another, they will succeed. 

Panicky woman on phone:
"My son is visiting you today, could you please pass him a message?"

Me, expecting an emergency:
"Of course, who do we need to ask for, and what is the message?"

Panicky woman on phone:
"He's XXX and the message is - Call your dad and tell him to pick your mum up at 2.30pm, same place he dropped her off, because I'm almost done shopping and I left my mobile phone in dad's car. I can't remember their mobile phone numbers you see, but found your number and knew you'd be able to help."

Me:
".... we'll bing bong for your son, and let him know..."